Talk: Pie Charts – Unloved, Unstudied, and Misunderstood

I gave a talk at Information+ earlier this year that has now been posted. It's about pie charts! And it was a fun talk, too.

The video is focused a bit too much on me at the beginning, so you'll miss a few of the early jokes. But for the most part, you'll see the (much more important) slides rather than me. This is the talk I made the materials for that I then posted in my pie charts study results walk-through.

There were some really good talks at Information+ – I will post a selection of links to videos here in a bit.

Robert Kosara is Senior Research Scientist at Tableau Software, and formerly Associate Professor of Computer Science. His research focus is the communication of data using visualization. In addition to blogging, Robert also runs and tweets. Read More…

Reader Interactions

Comments

I’m surprised you didn’t include 3D pie charts in your study (apparently). I’ve always suggested that segments further away are underestimated in value due to perspective, whereas the closer segments are overestimated. Any thoughts? I don’t hate pie charts, by the way, but I favour the unadulterated ones, properly sorted, not too many segments, etc. etc.

Excellent presentation, I very much enjoyed it. I’m curious though whether you did any research into the amount of time it took participants to read each visualization and come up with their answer? For example, I would guess that a donut might take slightly longer to interpret than a full pie chart because you are missing the additional visual cue of the angle. If that were the case then that would mean that a donut may well be a worse choice than a pie chart.

When comparing the relative effectiveness of different types of visualizations we often hear about cognitive vs pre-cognitive understanding, and are steered towards using visualizations that can be understood using the pre-cognitive parts of our brains. We’ve been told that pie charts aren’t very pre-cognitive and we have to study them a little longer to find the answers we need which, if true, is a major drawback. Based on this I’d be fascinated to see some data around the length of time it takes people to interpret different visualizations along with the scope for error.

Good questions! I believe we looked at time but found no statistically significant difference between pies and donuts. I’ll check with Drew on that, though (the data is also available btw).

As for pre-cognitive: there are certainly different amounts of effort, and that might be higher for pies than bars. Seems like something that has probably been studied, would be interesting to see some research.